Chapter 1 - Reactive Systems

Abstract

This chapter provides examples of reactive systems and contrasts them to transformational systems, listing the characteristics that divide reactive systems from transformational systems. The chapter also lists the four case studies that appear in many examples and describes the three additional case examples. Reactive systems perform state-based nonterminating processes that are interrupt-driven and that interact with the environment to enable, enforce, or prevent certain behavior in the environment. They may be subject to stringent real-time requirements and often perform several processes in parallel. Reactive systems may or may not need to handle large volumes of data, engage in complex behavior, or engage in many communications. Different reactive systems have different complexities along these dimensions and consequently different specification techniques are needed to design them. But in all cases, a reactive system designer needs techniques to specify stimulus-response behavior. Transformational systems perform terminating computations that, when terminated, do not leave the system in a significant state. Functional decomposition is a good design approach for transformational systems. Reactive systems, on the other hand, must be designed from the structure of the environment as well as from the desired system functionality.